I wasn't online when you experienced things, so I can't say. But next time it happens, look at the bottom of any page. You'll seee something like this:
Page generation time: 0.443s (PHP: 93% - SQL: 7%) - SQL queries: 21 - GZIP disabled - Debug on
Basically, this tells you how long the server took to do its thing. If the time listed is quick, but your response is slow, generally the problem lies somewhere between the C-Brat ISP and you, and there's nothing that can be done but wait.
When you start getting numbers over 5 seconds, the load on the server is creeping up. Whenever it is consistently over 10 seconds, and I notice it, I report it to the ISP after doing a little more homework.